This invention relates generally to a method for producing oil-soluble additives for lubricating oils.
Zinc dialkyldithiophosphates (ZDDP) are widely used as lubricant additives. The principal disadvantages of these compounds are that an ash residue is produced by the zinc as the additive is consumed, and that phosphorus is known to affect the efficiency of catalytic converters in motor vehicles, thereby causing emissions problems. Imidazolidinethione compounds useful as non-metallic lubricant additives, and processes for their production are disclosed in European Patent Application No. 1,229,023, published Aug. 7, 2002.
The problem addressed by this invention is to find improved processes for producing imidazolidinethione additives, including those disclosed in the aforementioned reference.